对-乙酰氧基苯甲酸与聚对苯二甲酸乙二醇酯共缩聚反应及醚键形成的研究

监测了对-乙酰氧基苯甲酸与聚对苯二甲酸乙二醇酯(PET)共缩聚反应过程中1HNMR图谱及特性粘度的变化,对乙酰氧基酯交换反应及乙酰脂肪酯的反应活性进行了研究。并研究了以低分子量PET或对苯二甲酸二乙二醇酯为原料时反应中醚键的形成及其进入共聚酯链的规律性。

Polycondensation Reaction of p-Acetoxybenzoic Acid and Poly(ethylene terephthalate) and the Formation of Ether Bonds

The transesterification reaction of acetates and etherification reaction during the polycondensation reaction of p-acetoxybenzoic acid (Ac-PHB)and poly(ethylene terephthalate)were studied by analyzing the reaction mixture sampled after different reaction time by ¹H NMRspectra and η] determination.Just in the beginning of the polycondensation reaction the PETchains degraded vigorously with the formation of acetoxy ethylene end groups of about 25% (molar ratio)of total ethylene content.Both the acetoxy ethylene and acetoxy phenylene end groups were reactive toward the polycondensation reaction.Using PETof low molecular weight or bis-hydroxyethylene terephthalate as the original material, the copolyester of high molecular weight could be prepared.However, it's T_f and HDTwere lower, and the solubility was higher than those as PETof high molecular weight was used.These poor properties of copolyester were explained by the high content of ethylene groups and the formation of ether bonds, among which the semi-aromatic ether content is much higher than the aliphatic one.Both the two ether bonds could react with carboxy end groups to propagate the chains under vacuum reaction condition .